Mobile communications networks are in the process of offering increasingly sophisticated capabilities associated with the motion and/or position location sensing of a mobile device. New software applications, such as, for example, those related to personal productivity, collaborative communications, social networking, and/or data acquisition, may utilize motion and/or position sensors to provide new features and services to consumers. Moreover, some regulatory requirements of various jurisdictions may require a network operator to report the location of a mobile device when the mobile device places a call to an emergency service, such as a 911 call in the United States. Such motion and/or position determination capabilities have conventionally been provided using digital cellular positioning techniques and/or Satellite Positioning Systems (SPS). Additionally, with the increasing proliferation of miniaturized motion sensors (e.g., simple switches, accelerometers, angle sensors, etc.), such on-board devices may be used to provide relative position, velocity, acceleration, and/or orientation information.
In conventional digital cellular networks, position location capability can be provided by various time and/or phase measurement techniques. For example, in CDMA networks, one position determination approach used is Advanced Forward Link Trilateration (AFLT). Using AFLT, a mobile device may compute its position from phase measurements of pilot signals transmitted from a plurality of base stations. Improvements to AFLT have been realized by utilizing hybrid position location techniques, where the mobile device may employ an SPS receiver that can provide position information independent of the information derived from the signals transmitted by the base stations. Moreover, position accuracy can be improved by combining measurements derived from both SPS and AFLT systems using conventional techniques. Furthermore, navigation devices often support popular and increasingly important SPS wireless technologies, which may include, for example, the Global Positioning System (GPS) and/or a Global Navigation Satellite System (GNSS). Navigation devices supporting SPS may obtain navigation signals as wireless transmissions received from one or more transmitter equipped satellites that may be used to estimate geographic position and heading. Some navigation devices may additionally or alternatively obtain navigation signals as wireless transmissions received from terrestrial based transmitters to estimate geographic position and heading and/or include one or more on-board inertial sensors (e.g., accelerometers, gyroscopes, etc.) to measure an inertial state of the navigation device. Inertial measurements obtained from these on-board inertial sensors may be used in combination with or independent of navigation signals received from satellite and/or terrestrial based transmitters and/or inertial sensors on a vehicle (e.g., accelerometers, gyroscopes, odometers, etc.) to provide estimates of geographic position and heading.
Although GNSS-based navigation systems can help users to navigate to destinations when users do not know or are uncertain about the routes to the destinations, there are many situations in which the positioning engine in a mobile device continues to operate even though the user may be traveling on a known road segment or the remaining journey to the destination is already known to the user. In at least these scenarios, a personal navigation device (PND) or other mobile device should be able to detect that the road segment or remaining journey to the destination is already known and act accordingly to improve user experience and reduce battery drain, which tends to be one of the most significant problems faced when using mobile devices in a navigation context (whether in a vehicular or pedestrian mode). For example, a mobile device that supports call and message handling tasks may be mounted in a car to perform navigation tasks and PNDs can likewise perform call and message handling tasks when connected to a suitable mobile device. Accordingly, one device (e.g., a mobile device or PND) can support navigation tasks in addition to call and message handling tasks, but users should focus on navigation tasks with high priority when traveling on unknown road segments or road segments that have substantial turns or other spatial characteristics that may require focused attention on driving over other non-navigation tasks. Furthermore, although existing navigation applications allow a device to reject incoming calls, any autoreply messages provided in response to the incoming calls are typically pre-set (e.g., “Hi, I am driving and will call you back”) or only provide limited information based on a current location (e.g., based on a speed and location output, an autoreply message may be “Hi, I am at <LOCATION> and will call you back later”). Accordingly, there exists substantial opportunities to reduce battery drain and otherwise improve user experience based on road segment familiarity or other navigation contexts that may have an impact on how much user attention may (or should) be required at a particular point in time.